1. Field of the Invention
The disclosure relates generally to systems and methods for network entry management, and, more particularly to systems and methods for network entry management that provide a hierarchical synchronization channel design for a multi-carrier system to reduce network entry latency.
2. Description of the Related Art
Recently, mobile stations, such as mobile devices having wireless communication capabilities have become more and more popular. Due to increased convenience and functions of the mobile devices, these devices have become basic necessities of life.
In a multi-carrier system, when a mobile station powers on, it will scan various carriers based on known channel rasters. In 3GPP 36.101 v9.0.0, the center raster is 100 kHz for all bands. A mobile station may scan synchronization channels on every 100 kHz in each band to discover if there is a 3GPP system. When a band 1 ranges from 2110 MHz to 2170 MHz, a mobile station will scan from 3GPP systems on the carriers 2110 MHz, 2110.1 MHz, 2110.2 MHz, . . . , 2169.9 MHz. Multi-carrier systems may be composed of fully configured carriers and partially configured/extension carriers. The fully configured carriers can operate standalone. The partially configured/extension carriers can not operate standalone, and can not be used for network entry. Currently, hierarchical synchronization channels (SCH) have been adopted by some orthogonal frequency division modulation (OFDM) systems, such as IEEE 802.16m and 3GPP LTE. Hierarchical SCH is composed of a primary synchronization channel (P-SCH) and secondary a synchronization channel (S-SCH). The P-SCH and S-SCH may be time division multiplexed. The P-SCH is used for timing acquisition and frequency synchronization, and is used for symbol boundary detection. The S-SCH may carry a cell identity (cell ID) or partial cell ID information, e.g. Physical ID in a 3GPP LTE. The S-SCH may be used for channel estimation.
Generally, a frame structure may include two P-SCHs and two S-SCHs, and a broadcasting channel (BCH) follows either the P-SCH or S-SCH. The BCH can carry system information, such as a bandwidth, identity, frame configurations, location of control channels, and other system information. The SCH is generally used as an identity for a station to lock onto the system. When a system adopts the hierarchical SCH, a mobile station may detect the P-SCH to synchronize system timing and center frequency, and then the mobile station will detect the S-SCH to acquire complete cell IDs. After, a mobile station can retrieve system information via the BCH. It is understood that, a mobile station will leave the carrier and scan for another carrier if the mobile station can not detect the P-SCH, S-SCH or BCH. It is noted that, a mobile station will scan every carrier within each band to try to lock onto the system. If no related information or mechanism can be provided in the hierarchical SCH, network entry latency will be serious.
IEEE C802.16m—08—1093 proposes a method to reduce network entry latency. It applies different P-SCHs to the fully configured carrier and the partially configured carrier. Therefore, a mobile station can detect the P-SCH to verify if a current carrier is the fully configured carrier. If the current carrier is a partially configured carrier, a mobile station will skip the carrier to scan for another carrier, such that network entry latency can be reduced. However, in IEEE C802.16m—08—1093, the number of P-SCHs has increased. If only three sequences are set for the P-SCHs, it will cause at least a 33% detection complexity overhead. The structure also wastes resources for the S-SCH.